1. Field of the Invention
The present invention relates to an intake silencer device which is formed integrally with an air cleaner and disposed upstream of a throttle body, in an intake passage in an engine.
2. Description of the Related Art
An intake silencer device integrally combined with an air cleaner mounted in an intake passage in an engine, is known from Japanese Patent Application Laid-Open No. 2-196157. In this intake silencer device, a side branch functioning as a resonant silencer is integrally defined in the air cleaner functioning as an expandable silencer, thereby reducing the noise of a lower frequency, while suppressing an increase in noise of a medium frequency.
The known intake silencer device includes Helmholtz-type silencers in an intake passage between the air cleaner and a throttle body and in a surge tank downstream of the throttle body, respectively, in addition to the side branch provided integrally with the air cleaner. When the plurality of silencers are disposed in the intake passage in the above dispersed manner, the entire intake silencer device is large-sized, resulting not only in an increased number of parts, but also in the possibility that the layout of the intake silencer device within a narrow engine compartment may be difficult. Moreover, the surface area of the entire intake silencer device is increased and liable to receive the heat of the engine. For this reason, the temperature of intake air passing through the intake silencer device is raised, and the resistance to the flow of the intake air is increased by the plurality of silencers disposed in the dispersed manner, resulting in the possibility that the engine power output may be reduced.